From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Axtens Date: Fri, 26 Feb 2021 05:44:39 +0000 Subject: Re: [PATCH v2 04/37] powerpc/64s: remove KVM SKIP test from instruction breakpoint handler Message-Id: <8735xj9yd4.fsf@linkitivity.dja.id.au> List-Id: References: <20210225134652.2127648-1-npiggin@gmail.com> <20210225134652.2127648-5-npiggin@gmail.com> In-Reply-To: <20210225134652.2127648-5-npiggin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Nicholas Piggin , kvm-ppc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org, Nicholas Piggin , Fabiano Rosas Nicholas Piggin writes: > The code being executed in KVM_GUEST_MODE_SKIP is hypervisor code with > MSR[IR]=0, so the faults of concern are the d-side ones caused by access > to guest context by the hypervisor. > > Instruction breakpoint interrupts are not a concern here. It's unlikely > any good would come of causing breaks in this code, but skipping the > instruction that caused it won't help matters (e.g., skip the mtmsr that > sets MSR[DR]=0 or clears KVM_GUEST_MODE_SKIP). I'm not entirely clear on the example here, but the patch makes sense and I can follow your logic for removing the IKVM_SKIP handler from the instruction breakpoint exception. On that basis: Reviewed-by: Daniel Axtens Kind regards, Daniel > > Reviewed-by: Fabiano Rosas > Signed-off-by: Nicholas Piggin > --- > arch/powerpc/kernel/exceptions-64s.S | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S > index a027600beeb1..0097e0676ed7 100644 > --- a/arch/powerpc/kernel/exceptions-64s.S > +++ b/arch/powerpc/kernel/exceptions-64s.S > @@ -2553,7 +2553,6 @@ EXC_VIRT_NONE(0x5200, 0x100) > INT_DEFINE_BEGIN(instruction_breakpoint) > IVEC=0x1300 > #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE > - IKVM_SKIP=1 > IKVM_REAL=1 > #endif > INT_DEFINE_END(instruction_breakpoint) > -- > 2.23.0